93P The International Clinical Outcome Study for Dysferlinopathy II: validation of motor outcome measures in a new patient cohort.

The International Clinical Outcome Study for Dysferlinopathy (COS) was the first multi-country natural history study in dysferlinopathy with the aim to characterise disease presentation and improve clinical trial readiness. In the absence of validated disease specific motor assessment scales, The North Star Assessment for limb girdle type muscular dystrophies (NSAD), was developed and validated in the COS I cohort. The Performance of upper limb (PUL 2.0), originally developed for DMD was assessed in COS I and found to be suitable to measure upper limb function in dysferlinopathy. The extension study, COS II, recruited 203 participants (119 new) from 16 sites in nine countries with the aim to validate the findings from COS I in an expanded cohort. We now examine the psychometric performance of the NSAD and PUL in the new COS II participants using Rasch Unidimensional Measurement Model (RUMM). Psychometric evaluation of 117 available assessments evaluated NSAD and PUL performance in seven areas: targeting, response categories, fit, reliability, dependency, stability and unidimensionality using RUMM2030 software. NSAD and PUL demonstrated unidimensional construct of functional motor performance and upper limb motor performance respectively, high reliability with a PSI of 0.96 and 0.95 respectively. A potential ceiling effect still existed for the strongest/ asymptomatic subjects in both scales. 27/29 items of the NSAD and 19/22 items of the PUL demonstrated ordered response categories, meaning the scoring categories for each item are logical and appropriate for dysferlinopathy. No items of NSAD with fit residuals outside ±2.5 but three on the PUL. The items fit well together to make use of the total score appropriate. Differential item functioning analysis, which indicates if a person factor influences the probability of scoring on an item was not present for gender on either scale. This study validated previous data from COS, confirming that the NSAD and PUL are suitable measurements for use in dysferlinopathy. Ongoing analysis is underway to examine the psychometric properties of these scales and responsiveness to change in functional ability over time. [ABSTRACT FROM AUTHOR]